Boeing says its Phantom Eye unmanned aircraft, burning liquid hydrogen as a fuel, has successfully completed its initial taxi test in California.

While it will someday soar to 65,000 feet, it took a modest, ground-level spin at Edwards Air Force Base in its first medium-speed taxi test this month, Boeing said Tuesday. It covered about 4,000 feet at speeds of up to 34.5 mph.

Additional taxi tests are scheduled, culminating with one at 46 mph, before the drone's first flight. Boeing has not announced a date for when it will go airborne, CNET.com reported.

"It's huge to capture the data that we did today," Drew Mallow, Phantom Eye program manager, said of the drone's taxi test, "to allow the team to evaluate it so we can fine-tune the models, understand if the software is correct and understand how the propulsion system is going to react as it moves forward."

Carrying 1,900 pounds of liquid hydrogen in its two tanks, the Phantom Eye is powered by 150-horsepower engines turning 16-foot-diameter propellers.

With a wingspan of 150 feet, the high-altitude, long-endurance unmanned aerial vehicle, with a 450-pound payload, is intended to stay aloft for four days on "persistent" intelligence, surveillance, reconnaissance and communications missions, Boeing said.